1. Field of the Invention
The present invention relates to a wireless communication apparatus, a wireless communication system employing the same and a control method thereof that uses a slot efficiently and enables communication between slave devices by selecting a temporary master device according to an amount of slot usage in the wireless communication apparatuses that are connected to the wireless communication system.
2. Description of the Related Art
FIG. 1 shows the structure of a Piconet in a typical Bluetooth communication system.
Referring to FIG. 1, the Bluetooth communication system has a plurality of slave devices S10, S20, S30 and S40 connected to one master device M10. Such a network, i.e., a network in which at least one slave device such as S10, S20, S30 and S40, is connected to one master M10, is called a Piconet. In the Piconet, a maximum of seven slave devices in an active state can be connected to the master device M10.
In the Piconet, the master device M10 and the slave devices S10, S20, S30 and S40 communicate through packets. FIG. 2(a) shows the structure of a conventional packet which is transmitted in the Piconet shown in FIG. 1, and FIG. 2(b) shows a header portion of the packet of FIG. 1 in greater detail.
The current Bluetooth communication method employs a master driven TDD (Time Division Duplex) type, system in which the master device transmits a packet designating a specific slave device, from a group of slave devices. The specific slave device subsequently transmits a data recorded packet to the master device as a response. Since the communication is carried out only between the specific slave device and the master device, the other slave devices cannot communicate with each other.
Therefore, several methods have been proposed to enable inter-slave communication, namely, peer-to-peer communication between slave devices.
One conventional method is a master-slave switching method. This method is performed between the master device and the slave device such that one of the slave devices acts as the master device thereby enabling communication with the other slave devices.
Another method is a destination address recording method, in which an address of a destination slave to which the packet should be finally sent, is recorded in an AM_ADDR (Active Member Address) part of the packet header area, and an address of a slave device which transmits the packet is recorded in a payload area of the packet.
FIG. 3 shows an example of the packet according to the destination address recording method. When one slave device sends an address of another slave device, desired for communication as recorded in the destination address, the master device analyzes the destination address of the received packet and transmits the packet to the corresponding destination. Accordingly, peer-to-peer communication is performed among the slave devices, albeit via the master device.
According to the destination address recording method, the master device analyzes and sends the received packets to the destination slaves every time the master device receives the packets. However, because communication among the slave devices is frequently carried out this method of slave to slave communication is time consuming and it wastes packets. This is because the destination address recording method requires more packets than are required for the communication between the slave and master devices.